1. Field of the Invention
The present invention relates to a liquid crystal display panel, and in particular, to a liquid crystal display panel in which a liquid crystal gap is secured by arranging spacers between transparent substrates.
2. Description of the Related Art
Liquid crystal display panels (LCDs) are used as display devices of a variety of portable information devices such as cellular phones, personal digital assistants (PDAs), digital cameras and multimedia players.
The liquid crystal display panel comprises a liquid crystal encapsulated between a pair of transparent substrates made of glass, resin or the like and performs the image display by driving and controlling the liquid crystal molecules by use of an electric field. One of the transparent substrates is used as an array substrate having a surface on which a plurality of thin-film transistors (TFTs) are arranged in an array. The other transparent substrate is used as a color filter substrate having a surface on which a black matrix (BM) and color filters are arranged.
In recent liquid crystal display panels, it has become common to maintain the substrate distance between the two transparent substrates (liquid crystal gap) by arranging spacers between the substrates. However, low-temperature bubble defects and unevenness in brightness by pressure occur even in such liquid crystal display panels having the spacers between the transparent substrates, and thus countermeasures for preventing the low-temperature bubble defects and the unevenness in brightness by pressure are being requested. The low-temperature bubble defects are display defects caused by vacuum bubbles (low-temperature bubbles) forming in the liquid crystal layer when the substrate distance cannot change smoothly following the volume contraction of the liquid crystal in a low-temperature environment. The unevenness in brightness by pressure is a display defect occurring in regions of the liquid crystal display panel where the substrate distance has become nonuniform due to external pressure locally applied to a surface of a transparent substrate.
Technologies for preventing the low-temperature bubble defects and the unevenness in brightness by pressure by arranging columnar spacers differing in the height have been disclosed in JP-A-2002-341354, JP-A-2003-84289, and JP-A-2003-121857. Specifically, the low-temperature bubble defects are prevented by allowing the substrate distance to decrease flexibly due to elastic deformation of the higher spacers. The unevenness in brightness by pressure is prevented by inhibiting excessive decrease in the substrate distance by having both the higher spacers and the lower spacers receive the applied load.